Biology Class 11 NCERT Solutions: Chapter 22 Chemical Coordination and Integration Part 2

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Q: 1. Fill in the blanks:

Hormones Target gland

(A) Hypothalamic hormones __________________

(B) Thyrotrophin (TSH) __________________

(C) Corticotrophin (ACTH) __________________

(D) Gonadotrophins (LH, FSH) __________________

(E) Melanotrophin (MSH) __________________

Answer:

Hormones Target gland

(A) Hypothalamic hormones: Pituitary

(B) Thyrotrophin (TSH): Thyroid

(C) Corticotrophin (ACTH): Adrenal

(D) Gonadotrophins (LH, FSH): Ovary, Testis

(E) Melanotrophin (MSH): Melanocyte

Q: 5. Write short notes on the functions of the following hormones,

(A) Parathyroid hormone (PTH)

(B) Thyroid hormones

(C) Thymosins

(D) Androgens

(E) Estrogens

(F) Insulin and Glucagon

Answer:

(A) Parathyroid hormone (PTH) – The parathyroid hormone is secreted by the parathyroid gland. Its main function is to increase the level of calcium in blood. It promotes the reabsorption of calcium from nephrons and also, promotes the absorption of calcium from digested food. Hence, it plays an important role in maintaining calcium balance in the body.

(B) Thyroid hormones – Thyroid hormones such as thyroxine, triiodothyronin, and thyrocalcitonin are secreted by the thyroid gland.

Thyroxine maintains the basal metabolic rate of the body and regulates the carbohydrate, fat, and protein metabolism. Water and electrolyte balance is also maintained by thyroid hormones. Thyrocalcitonin or calcitonin lowers calcium level in blood plasma. It plays a significant role in calcium levels along with parathyroid hormone.

(C) Thymosins – Thymosin is secreted by the thymus gland. It plays a major role in protecting the body against infectious agents. It helps in the differentiation of T-lymphocytes and also promotes the production of antibodies. Hence, it provides both cell-mediated and humoral immunity. Thymosins also help in the development of sex glands.

(D) Androgens – The leydig cells of testis produce androgens such as testosterone. Testosterone is a male sex hormone that regulates the development of secondary sex characteristics such as facial hair, hoarse voice, development of reproductive organ, etc. Androgens also regulate the development, maturation, and functions of various male accessory organs such as epididymis and prostate glands. It stimulates spermatogenesis and formation of mature sperms. It also influences male sexual behavior.

(E) Estrogens – Estrogen is the female sex hormone that controls the development of secondary sex characteristics such as enlargement of breasts and development of female reproductive organs. It plays a role in the development, growth and maturation of female secondary sex organs. It also helps in the development of growing ovarian follicles. It influences female sexual behavior.

(F) Insulin and glucagon – Glucagon and insulin are secreted by cells of pancreas. They regulate the blood glucose level in the body.α-cells secrete glucagon that increases the blood glucose. Level to normal in hypoglycemic condition in body, whereas β-cells secrete insulin that lowers the blood glucose level to the normal in Hyperglycemic condition in body and initiates the of glycogen from excess glucose by liver cells.

Insulin also prevents the formation of glucose from non-carbohydrate substances such as proteins and fats. Hence, it acts as a regulator of carbohydrate metabolism.

Function of glucagon – The main function of the glucagon is to increase the level of glucose when there is a deficiency of glucose in the body. This process is known as glycogenolysis.

Q: 6. Give example(s) of:

(A) Hyperglycemic hormone and hypoglycemic hormone

(B) Hypercalcemic hormone

(C) Gonadotrophic hormones

(D) Progestational hormone

(E) Blood pressure lowering hormone

(F) Androgens and estrogens

Answer:

(A) Hyperglycemic hormone and hypoglycemic hormone:

Hyperglycemic hormone is glucagon, while hypoglycemic hormone is insulin.

(B) Hypercalcemic hormone:

Parathyroid hormone (PTH) is hypercalcemic hormone.

(C) Gonadotrophic hormones:

Luteinizing hormone and follicle stimulating hormones are examples of gonadotrophic hormone.

(D) Progestational hormone:

Progesterone is a presentational hormone.

(E) Blood pressure lowering hormone:

Nor-adrenalin is a blood pressure lowering hormone.

(F) Androgens and estrogens:

Testosterone is an example of androgen, while an example of estrogen is estradiol.